1. Field of the Invention
Embodiments of the present invention generally relate to semiconductor processing apparatus. In particular, embodiments of the invention relate to a multi-substrate transfer robot and semiconductor processing system for high throughput processing of semiconductor wafers.
2. Description of the Related Art
The growth of silicon-containing epitaxial films has become increasingly important due to new applications for advanced semiconductor devices. Such films may be grown selectively or non-selectively (blanket deposition) on the substrate. By selective growth it is generally meant that an epitaxial film is grown at specific locations on a substrate having device feature patterns already incorporated therein. For example, the substrate may include patterns for gate electrodes, spacers, ultra-shallow junctions, or other features. To avoid damaging such device features during fabrication, it may be desirable to use lower temperature processes during epitaxial film growth.
The desire for lower process temperatures has led to the development of the low or reduced pressure chemical vapor deposition (LPCVD or RPCVD; herein after to be referred to as LPCVD) epitaxial reactor. Deposition at lower pressures allows lower temperatures to be used while improving film uniformity. In one example of LPCVD epitaxial silicon deposition, the reactor deposition temperature may range from about 600 degrees Celsius to about 1100 degrees Celsius, and the deposition pressure may range from about 10 Torr to 100 Torr. However, lower process temperatures can slow chemical reaction rates which can adversely affect film properties.
In epitaxial films, lack of uniformity can lead to poor device performance. Gas flow dynamics help determine the thickness uniformity. Certain epitaxial processes may take place at lower temperatures so that reaction kinetics control the deposition rate. In this case, temperature more strongly influences both thickness and resistivity uniformity. However, gas flow will still affect thickness.
The desire for better control of gas flow dynamics and substrate temperature has led to the development of the single substrate LPCVD epitaxial reactor chamber which uses radiant heating. Batch processing of many substrates creates variation in temperature and gas flow across each substrate within the batch, and from batch to batch. The use of radiant heating in the single substrate reactor allows a more uniform temperature profile across the substrate surface, and the gas flow dynamics can be more precisely controlled for a single substrate so that the distribution of reactant material over the substrate is more uniform.
Unfortunately, a single substrate processing reactor cannot match the throughput of a batch (over 50 substrates), mini-batch (about 25-50 substrates), or micro-batch (less than 25 substrates) LPCVD epitaxial reactor. Additionally, the use of radiant heating during selective epitaxial deposition can lead to temperature variations across the substrate surface since the emissivity of a substrate is highly dependent on the thin film structures and materials on the substrate surface.
Therefore, there is a need for a low temperature epitaxial deposition reactor with increased throughput that can provide improved substrate temperature uniformity and more uniform process gas flow across the substrate surface.
Additionally, the exchange of substrates is critical for maintaining high throughput in such applications. Conventionally, such exchanges are performed by substrate transfer robots that may carry a single substrate at a time. Unfortunately, such single-substrate transfer limits the exchange rate of substrates.
Therefore, there is a need for substrate transfer robots capable of high throughput substrate exchanges.